Related art has been proposed such as a traction control device for a vehicle that is disclosed, for example, in Japanese Patent Application Laid-Open No. HEI 07-132761. The traction control device disclosed in this publication is provided with a differential for transmitting power from an automatic transmission to right and left driving wheels. This traction control device calculates a brake torque to be applied to the driving wheels by: detecting a torque input to the differential; calculating a critical drive torque based on an input torque at the time when excessive slipping of one of the driving wheels is detected; and subtracting this critical drive torque from a current input torque to obtain the brake torque.
In the traction control device of the related art, the brake torque to be applied to the driving wheels is set with high priority assigned to the suppression of wheel slip. Therefore, inefficient utilization of torque originally generated by the engine may sometimes make it impossible to obtain sufficient driving force. For example, in a case where a target vehicle speed is calculated while the vehicle travels at a low speed, an engine revolution corresponding to the target vehicle speed is considerably low. Accordingly, the critical torque is considerably small. Thus, the torque originally generated by the engine is almost entirely cancelled out by braking. In this case, it is impossible to obtain sufficient engine torque. In particular, the insufficiency of engine torque is conspicuous in the case of a vehicle that generates low engine torque, for example, a vehicle with a small displacement engine.